Explosive composition containing an inorganic oxidizer salt,a soluble lignosulphonate,and mutual solvent therefor



United States Patent 3,369,945 EXPLOSIVE CGMPCSITION CONTAINING ANINORGANEC OXIDLZER SALT, A SOLUBLE LEGNSSULFHONATE, AND MUTUAL SOL- VENTTHEREFOR Joseph Francis McLean Craig, Beloeil, Quebec, and Errol LintonFalconer, St. Hilaire, Quebec, Canada, assignors to Canadian IndustriesLimited, Montreal, Quebec, Canada, a corporation of Canada No Drawing.Filed Oct. 14, 1966, Ser. No. 586,676 Claims priority, application GreatBritain, Nov. 1, 1965, 46,133/65 8 Claims. (Cl. 149-39) ABSTRACT OF THEDISCLGSURE In lurry-type explosive compositions comprisingoxygen-supplying salts, a fluid carrier and a sensitizer or fuel,optimum detonation and propagation has heretofore been possible onlythrough the use of relatively large quantities of sensitizing materialsand fuels. The present invention provides an explosive slurrycomposition of improved sensitivity, especially in small diametercharges, by incorporating in the composition a quantity of a solublelignosulphonate which permits a reduction in the fuel and/or sensitizercontent.

This invention relates to explosive compositions comprising essentiallyan inorganic oxygen-supplying salt, a sensitizer, a fuel, a thickenerand a mutual solvent for the inorganic salt and the sensitizer. Inparticular, the invention relates to a means whereby the sensitivity ofsuch explosive compositions may be substantially improved.

Explosive compositions comprising an oxygen-supplying salt such as, forexample, ammonium nitrate, and a sensitizer and/or fuel together with afluid solvent, disperser or carrier such as water, are known. Thesecompositions are commonly referred to as slurry explosive compositionsor, more generally, as slurry explosives. Such slurry explosives mayrange in degree of firmness or consistency from highly viscous,plastic-like extrudable compositions to less viscous pumpable orpourable fluidlike mixtures.

Slurry explosive compositions of the aforementioned types normallycontain as essential ingredients widely known sensitizing and powerenhancing materials and fuels such as, for example, finely divided.light metal, finely divided carbon and the like. In some cases, it isadvantageous to add a self-explosive ingredient such as particulate TNT,PETN or smokeless powder to further improve the ensitivity or strengthor both of the slurry explosives and thereby insure detonation andpropagation. A wide range of such compositions are now known to the art.

For optimum reliability the known sensitizers employed in slurryexplosives are either self-explosives or relatively expensive materialssuch as very finely divided light metal powders. Without suchsensitizers, these slurry explosive compositions tend to be detonableonly in large diameter charges with large primers. It has thus beennecessary for the manufacturer of explosives to employ relatively largequantities of sensitizing material and fuel in slurry explosives inorder to insure detonation and propagation. Such compositions, as wellas being relatively expensive, are hazardous to handle and requirespecial and costly precautions in manufacture, transportation, storageand use. Slurry explosive compositions containing self-explosives are,in turn, in most jurisdictions subject to regulatory restrictions intransportation and storage. Those that contain reactive sensitizers suchas, for example, paintfine aluminum powder, tend to deteriorate and losesensitivity on storage.

It has now been found that the aforementioned disadvantages may beovercome by employing as a sensitizer in slurry explosive compositions asoluble lignosulphonate.

It is, therefore, an object of the present invention to provide a meanswhereby the sensitivity of a slurry explosive composition may beincreased.

Another object of the invention is to provide a slurry explosivecomposition which may be detonated in boreholes of small diameter.

Another object of the invention is to provide a sensitive slurryexplosive composition which is devoid of any selfexplosives or otherhazardous material.

A further object of the invention is to replace the known reliablesensitizers in slurry explosive compositions with a sensitizer that ismuch less costly and easily available.

Yet another object of the invention is to provide a sensitive slurryexplosive composition that is stable and that does not deterioratephysically or become insensitive during storage.

These and other objects of the invention will become apparent from aconsideration of the following description and claims.

The improved explosive composition of this invention comprisesessentially at least one inorganic oxygensupply salt, at least onesoluble lignosulphonate, a fuel, a thickener and a mutual solvent forthe inorganic salt and the lignosulphonate.

The addition of a soluble lignosulphonate to a slurry explosivecomposition has the surprising and desirable effect of substantiallyincreasing the sensitivity of the composition.

It is thus now possible to prepare useful and powerful, slurry explosivecompositions which, though devoid of any self-explosive ingredient, maybe detonated with ease in boreholes of small diameters. It is similarlynow possible to prepare such compositions even containing additionalsensitizing material such as, for example, finely divided aluminium,aluminium alloy, silicon, ferrosilicon or ferrophosphOrus orself-explosives which are more reliable to detonation and propagationthan heretofore and which may be detonated in smaller diameter and withthe use of smaller priming charges that has heretofore been possible.

Preferred blasting slurry explosive compositions of this inventioncontain from 30 to 90% by weight of at least one inorganicoxygen-supplying salt, from 0.1 to by weight of a solublelignosulphonate from 1 to 3 by weight of a mutual solvent for theinorganic salt and the lignosulphonate from 0.1 to 10% by weight ofthickener and from 0 to 40% by weight of fuel the proportions of theingredients being such that the oxygen balance of the total compositionis from +15 to 35 grams of oxygen per 100 grams of finished explosive.

A preferred inorganic oxygen-supplying salt for inclusion in theexplosive compositions of this invention is ammonium nitrate. It is insome cases advantageous to replace some, suitably up to 50% or even upto of the ammonium nitrate by other metal nitrates such as sodium,barium, potassium and calcium nitrates. The particle size of theinorganic oxygen-supplying salts is not critical and powdered,granulated, or prilled forms may be used and part of the salts may bepredissolved in all or part of the solvent.

A preferred mutual solvent for the oxidizing salt and the solublelignosulphonate is water. However, other suitable mutual solvents suchas, for example, formamide and dimethyl sulphoxide (DMSO) may be used inproportions up to total replacement of the water. Ethylene 3 glycol maybe used in proportions up to 50% replacement of the water. These organicsolvents are polar liquids, readily miscible with water in allproportions and are effective solvents for ammonium nitrate and otherinorganic salts.

Where employed, the aluminium or aluminium alloy or other energeticmetal or metallo-ids suitable for use in the explosive composition ofthis invention must be in finely divided form and may most suitablyrange from a fine dust to a form not coarser than that which will passthrough a size 6 Tyler mesh screen. For example, relatively inexpensiveair-atmozide aluminium powder, shredded foil or granules made fromreclaimed scrap are suitable types. The use of the expensive paint-finealuminium is not required to achieve high sensitivity in the explosivecomposition of this invention.

Useful particulate self-explosives which may be used in the explosivecomposition include, for example, trinitrotoluene (TNT) pentaerythritoltetranitrate (PETN), cyclotrirnethylenetrinitramine (RDX), composition B(mixture of TNT and RDX), pentolite (mixture of PETN and TNT), smokelesspowder, nitrocellulose and mixtures of these.

The gel-forming or thickening agents employed in the aqueous slurry formof the explosive of the invention are preferably mannogalactans such asguar gum or carab seed. Guar gum of the self-cross-linking type recentlymade available on a commercial scale may be suitably employed. Whereeither dimethyl sulphoxide or formamide is employed alone as the mutualsolvent in the slurry, hydroxyethyl cellulose may be used as a suitablethickener. Where dimethyl sulphoxide, formamide or ethylene glycol isused in combination with water, guar flour, tamarind flour or starch aresuitable thickeners. A number of modified and synthetic materials usefulas thickeners can be selected which are appropriate to the solventsemployed and will be obvious to those skilled in the art. v

Metallic ch'romates suitable for use as cross linking agents for thepolysaccharides in aqueous slurries are the same as those disclosed inCanadian Patent No. 729,555, issued on Mar. 8, 1966, that is, a metallicchromate selected from the group consisting of sodium and potassiumdichromate and zinc and barium chromate.

The soluble lignosulphonate sensitizers may be any one of the wide rangeof lignin sulphonates commercially available. Any soluble salt of ligninsulphonic acid may be used and calcium, sodium and ammoniumlignosulphonates have been found particularly suitable in the explosivecomposition of the invention. Such lignin sulphonates are by-products ofthe pulp and paper industry and are produced from waste sulfite liquor.The lignosulphonates may be employed either as a dry powder oralternatively as a solution. Where a lignosulphonate solution isemployed, for example, an aqueous solution, the water of solution may beemployed as all or part of the aqueous medium of the explosivecomposition.

The explosive composition may be prepared by processes well known in theart employing simple mixing procedures, the soluble lignosulphonatesensitizer being added at any convenient stage in the manufacture. Theligniosulphonate sensitizer may similarly be employed where a slurryexplosive composition is prepared for use at the blasting site by meansof the now well known slurry mix truck.

The following examples and tables illustrate the improved explosivecomposition of this invention but the latter is in no manner to belimited in scope to the embodiments described.

Example 1 An extrudable gelatinous explosive composition containing asessential ingredients ammonium nitrate, sodium nitrate, water,particulate TNT and particulate PETN was prepared. Additional softeningor gelling material was also included in the composition. An 8"cartridge of 1 /2" diameter failed to be detonated with one No. 8blasting cap. Two similar compositions in the same cartridge sizecontaining in addition 0.5% by weight of sodium lignosulphonate and 1.0%by weight of ammonium lignosulphonate respectively were successfullydetonated with one No. 8 blasting cap. The results are summarized inTable I, the quantities shown being expressed as percent by weight ofthe total.

TABLE I Mix No 1 2 3 4 Particulate PETN 10.0 10.0 4. 6 Particulate TNT20.0 20. 0 20.0 23.0 Graincd ammonium nitrate 30. 0 30. 0 60. 0 34. 3Grained sodium nitrate 33.0 33. 0 14. 0 e 31.0

1. 4 1. 4 1. 3 1. 6 Guar flour... O. 4 0. 4 0. 5 0. 4 Tamarind fl0ur. 0.4 0. 4 0. 4 Sulphur 0. 7 Sodium lignosulphonate 0. 5 Ammoniumlignosulphonate. 1.0 Oxygen balance +2. +2. 9 +0. 9 +0. 8 Detonation 1Failed 1 No. 8 cap. 2 Fired 1 No. 8 cap. 3 Fired 5 No. 8 caps.

As can be seen from the above results Mix 1, devoid of lignosulphonatefailed with one No. 8 cap while Mix 4, similarly devoid oflignosulphonate required five No. 8 caps for detonation. Mixes 2 and 3containing lignosulphonate fired with a single No. 8 cap.

Example 2 TABLE 11 Mix No 1 Ammonium nitrate 5 Water 1 Paint-finealuminium Calcium nitrate Carbon black Guar flour Ammoniumlignosulphonat Oxygen balance Detonation 1 Failed with 1 No. 8 cap in 2tests. 2 Fired with 1 No. 8 cap.

As can be seen from the above results Mix No. 1 containing sensitizingmaterial but devoid of lignosulphonate failed to detonate while asimilar mix containing ligno sulphonate was initiated with a single N0.8 cap.

Example 3 An aqueous slurry explosive composition containing asessential ingredients, oxygen supplying salts, water, aluminium powder,pelleted TNT and thickener was prepared. A quantity of ammoniumlignosulphonate was added to one batch of the composition, the otherbatch being devoid of lignosulphonate. The respective mixtures werepackaged in 24 inch cartridges of 3 /2 inch diameter and exposed toinitiation by 60 gram pentolite primers. The

compositions failed. The results are summarized in Table ities V below,the quantities being expressed as percent by Weight of the total.

TABLE V lignosulphonate failed to detonate.

ight of the total.

TABLE III mixture containing no The results are summarised in Table III,the quant being expressed as percent by We Mix N0.

Example 7 A series of five aqueous slurry explosive compositions wereprepared containing as essential ingredients oxygensupplying salts,water, a fuel and a thickener. A range of lignin sulphonic acid saltswas added to the compositions and each was cartridged and exposed toinitiation by pentolite primer. In all cases detonation occurred and inone instance (Mix No. 5, Table VII) detonation was achieved in verysmall diameter charge. In all cases detonation of -a high order ofdetonation velocity resulted. The results are summarized in Table VII,the quantities shown being expressed as percent by weight of the total.

TABLE VII Mix N Ammonium nitrate Aluminum powder Sodium nitrate C alciumlignosulphonate (dry) 9. 0 C aleiumlignosulphonate (50% solution).Sodium lignosulphonate Ammonium lignosulphonate (49% soluon Oxygenbalance. 29 -24 Density (gm /cc) 1.45 1.44 Cartridge size 6 x 24" x 24Pentolite primer (g.) 680 680 Detonation velocity, M/S 1 3,110 1 4,400

1 Unconfined. 2 Confined in steel pipe.

Example 8 TAB-LE VIII Mix No 1 2 Particulate TNT 10. O 10. 0 Ammoniumnitrate 39. 0 37. 0 Sodium nitrate 8. 0 8.0 15. 5 15. 5 25. 0 25. 0 1. 5l. 5 1 0 1. 0 2. 0 24. 1

450 Detonation Fired Example 9 A series of slurry explosive compositionswere prepared wherein a part or all of the normally used water Table IX,the quantities shown being expressed as percent by weight of the total.

TABLE IX Mix No Ammonium nitrate (AN) Sodium nitrate Pelleted TNT.Granular PETN- Tamarind flour- Pregelled starch. Hydroxyethyl cellulWater Ammonium lignosulphonate;

Density (gm/cc.) Minimum primer required 1:112 liquid at 25 C. 2 5 No. 8caps.

! 1 No. 6 cap.

4 10 gm. pentalite.

Example 10 A series of explosive compositions were prepared wherein apart of the normally used Water solvent was replaced with for-mamide.The balance of the ingredients consisted essentially of oxygen-supplyingsalts and finely divided metal fuel together with known thickeners ordensity controllers. Quantities of ammonium lignosulphonate werecontained in one group of compositions and a second group was devoid oflignosulphonate. Both types of compositions were packaged in cartridgesof various diameters and exposed to initiation by various primers. Thecompositions containing lignosulphonate required sub stantially lessprimer initiation than did the non-lignosulphonate-containingcompositions. The results are summarized in Table X, the quantitiesshown being expressed as percent by weight of the total.

TABLE X Ammonium nitrate- 71. 67. 0 Sodium nitrate" 8. 0 8.0 UreaFormamide 4. 0 4. 0 Granular aluminium.. 4. 0 4. 0 Air atomizedaluminium. Ferrosilicon Gilsonite.--- 2. 2. 5 Sugar....- 4.0 Glyc 1. 0Guar flour (thickener)- 0. 5 0. 7 0. 5

. l0. 0 l2. 8 10. O Ammonium lignosul honate- 7. 0 Density (gin/cc.) 1.41 1.34 1.50 Cartridge diameter (inch)-... 6 6 6 Minimum primer required(g 1 320 320 1 680 1 Failed.

Example 11 Example 13 Two slurry explosive compositions were preparedwherein part of the normally used water solvent was replaced withdimethyl sulphoxide (DMSO). The balance of the essential ingredientsconsisted of oxygen supplying salts and known fuels, thickeners andstabilizers. To one of the compositions was added a quantity of ammoniumlignosulphonate sensitizer. Packaged in 2 /2 inch and 3 inch diametercartridges the lignosulphonate-containing composition was detonated by a160 gm. pentolite primer while the composition devoid of lignosulphonatefailed to detonate. The results are summarized in Table XI, thequantities shown being expressed as percent by weight of the total.

TABLE XI MixNo Ammonium nitrate Sodium uitrate.-..

1 Use to eliminate any large unstable air bubbles in the mix.

2 Detonation catalyst.

3 A similar composition using water solvent and devoid of DMSO was lesssensitive.

Example 12 A field trial was carried out at an iron ore mine using alignosulphonate sensitized aqueous slurry. The composition, prepared bya slurry mix pump vehicle, is shown as Mix 1 in Table XII below. It wasloaded into 5 boreholes each filled with water. Each borehole was 9%"diameter x 42' deep. After days all the boreholes detonatedsuccessfully. Approximately 5,700 pounds of explosive compositions wereloaded and initiated with 1 /2 pound pentolite primers. A similarcomposition but devoid of lignosulphonate was prepared as shown in TableXII, Mis 2. A cartridge 10" in diameter x pounds primed with 680 gramsof pentolite failed to detonate. The results are summarized in TableXII, the quantities shown being expressed as percent by weight of thetotal.

TABLE XII Mix No Zinc ehromate Water Oxygen balance- Density (gm./cc.).Detonation ivwas gz rew pre CA) on (DQOKIOOS KIMO Q.

ayne TAB LE XIII Sample No 1 2 Ammonium nitrate 35. 0 Sodium nitrate16.0 Water 14. 0 Ethylene glycol Guar flour (thickener)-- 0. 5 Ammoniumlignosulpho 4. 5 Aluminium granules... 29. 0 Air atomized aluminiumPaint-fine aluminium..... l 0

Segregation of ingredients I 1 Nil after 30 days storage. 2 Nil after 79days storage.

As may be seen from the results shown in the preceding examples andtables, the addition of a soluble lignosulphonate to a slurry explosivecomposition has the surprising eifect of substantially increasing thesensitivity of the compositions. Slurry explosives of this type havingan oxygen balance outside the range of +15 to 35 grams of oxygen pergrams of finished explosive have failed to detonate consistently. It ispreferred, therefore, that quantities of lignosulphonate sensitizer andfuel used be such that the oxygen balance of the composition is Withinthe range +15 to -35.

It will be appreciated by those skilled in the art that the principaladvantage to be enjoyed through the use of the lignosulphonatesensitized slurry explosive compositions of the invention lies in theutilization of nonself-explosive slurry composition. That is, slurrycompositions comprising oxygen-supplying salts, a solvent for theoxygen-supplying salts and a fuel may now, by the addition of a suitablequantity of lignosulphonate, be employed as practical and reliablecommercial explosives possessing the additional advantages of low costand great handling safety. Where it is desired to include in suchcompositions additional strength ingredients such as powdered lightmetal fuels or self-explosives, the use of the lignosulphonatesensitizers provides compositions which may be detonated in smallerdiameter charges or with lower strength primers than has heretofore beenpossible.

It has also been found that the use of lignosulphonate sensitizers hasno detrimental effect on the storage properties of aqueous slurrycompositions; that is, compositions senitized with lignosulphonate willshow no greater breakdown or segregation of ingredients than willsimilar compositions devoid or lignosulp'honate. As is well known, thepresence of undesirable material such as, for example, impurities inpowdered light metal in a slurry explosive has the effect of causing thecomposition to break down over long periods of storage into solids and asupernatent liquid layer. The use of lignosulphonate in no wayaccelle'rates this breakdown and may, in fact, provide a usefulstabilizing function in such compositions. It has been noted that wherelignosulphonates are employed as sensitizers in aluminum-cntainingslurry explosives, the use of stabilizers normally employed in suchcompositions is unnecessary.

The lignosulphonate sensitizers additionally function as effectiveagents in preventing or arresting the dissipation of minute bubbles ofair which have been entrained or entrapped in the slurry mixture. Suchair bubbles are normally incorporated in slurry explosive compositionsby the lifting and folding of the mixture which occurs during theoperation of the mechanical mixing of the ingredients or, alternatively,air is introduced into the mixture along with the dry ingredients. Thequantity of such entrapped air provides a useful function in controllingthe density of the explosive compositions.

What we claim is:

1. An explosive composition comprising essentially at least Oneinorganic oxygen-supplying salt, a soluble lignosulphonate, a mutualsolvent for the inorganic oxygensupplying salt and the solublelignosulphonate, a thickener and a fuel, the proportions of theingredients being such that the oxygen balance of the total compositionis from about +15 to. about -35 grams of oxygen per -100 grams offinished explosive.

2. An explosive composition as claimed in claim 1 wherein the fuel isselected from the group consisting of carbonaceous material, particulatenitrated organic explosive, particulate light metal or metalloids,sulphur, carbon, urea and mixtures thereof.

3. An explosive composition as claimed in claim 1 wherein the mutualsolvent is selected from the group 12 consisting of water, formamide,dimethyl sulphoxide and mixtures thereof.

4. An explosive composition as claimed in claim 1 wherein the mutualsolvent comprises a mixture of water and ethylene glycol in proportionssuch that the ethylene glycol represents not more than by weight of thetotal solvent.

5. An explosive composition as claimed in claim 1 wherein the oxygensupplying salt is selected from the group consisting of the nitrates ofammonia, sodium, potassium, barium, calcium and mixtures thereof.

6. An explosive composition as claimed in claim 1 wherein the solublelignosulphonate is selected from the group consisting of calcium, sodiumand ammonium lignosulphonate and mixtures thereof.

7. An explosive. composition as claimed in claim 2 wherein theparticulate nitrated organic explosive is selected from the groupconsisting of trinitrotoluene, pentaerythritol tetranitrate,cyclotrimethylenetrinitramine, a blend of trinitrotoluene andcyclotrimethylenetrinitramine, a blend of trinitrotoluene andpentaer'ythritol' tetranitrate, smokeless powder, nitrocellulose andmixtures thereof.

8. An explosive composition comprising essentially between about 30% andabout by weight of an inorganic oxygen-supplying salt, between about0.1% and 25% by weight of a soluble lign'osul'phon-ate, from about 1% toabout 30% by weight of a mutual solvent for the inorganicoxygen-supplying salt and the soluble'lignosulphonate, from about 011%to about 10% by weight of a thickener and from 0 to 40% by weigh-t of afuel, the oxygen balance of the total composition being from about +15to about 35 grams of oxygen per grams of finished explosive.

References Cited UNITED STATES PATENTS 3,132,061 5/1964 Walsh et a114941 CARL D. QUARFORTH, Primary Ex'aminer.

S. I. LECH'ERT, 111., Assistant Examiner.

